5 results
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2. Tensile and Deformation Behavior of Auxetic Plied Yarns.
- Author
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Ng, Wing Sum and Hu, Hong
- Subjects
- *
DEFORMATIONS (Mechanics) , *TENSILE strength , *YARN , *AUXETIC materials , *POISSON'S ratio - Abstract
This paper presents an experimental study of tensile and deformation behavior of an auxetic plied yarn structure. The basic configuration of the plied structure formed with two soft yarns and two stiff yarns was firstly introduced. Based on this 4-ply helix structure, six kinds of yarn samples were made by different combinations of soft yarns, stiff yarns and twist levels. These yarn samples were first tested and the effects of different design parameters were analyzed. Apart from the tensile test, changes in the internal structure of two samples upon stretching were also studied through microscopic examination. Finally, double helix yarn and 6-ply auxetic yarn were made for a comparative purpose to investigate the effect of helical structure. The study shows that all of the 4-ply auxetic yarn samples exhibit negative Poisson's ratio (NPR) throughout the entire tensile process, and the magnitude of NPR gets larger with a smaller soft yarn diameter, a higher tensile modulus of stiff yarn and a lower twist level. The study also shows that auxetic behavior inside the 4-ply structure is generated by the interplay between the soft yarns and stiff yarns and 4-ply auxetic yarns have the advantages to produce immediate auxetic effect upon stretching. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
3. The Elastic Uniaxial Properties of a Center Symmetric Honeycomb with Curved Cell Walls: Effect of Density and Curvature.
- Author
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Harkati, El Haddi, Daoudi, Nour El‐Houda, Abaidia, Chames Eddine, Bezazi, Abderrezak, and Scarpa, Fabrizio
- Subjects
- *
ELASTICITY , *POISSON'S ratio , *FINITE element method , *DEFORMATIONS (Mechanics) , *TRUSSES - Abstract
We propose in this paper analytical and numerical models that describe the in-plane uniaxial elastic properties (Young's moduli and Poisson's ratios) of a honeycomb structure with curved walls. We perform a parametric analysis of the mechanical performance of this honeycomb also by taking into account the different types of deformations acting inside the cell walls. The curved wall honeycomb possesses higher magnitudes of the Poisson's ratio ν12 in the auxetic configuration compared to classical center symmetric configuration with straight cell wall. The presence of the curvature also allows creating configurations with positive Poisson's ratio even for negative internal cell angles, and makes this honeycomb design attractive for mechanical tailoring. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
4. Auxetic structures with regularly configured rigid sliding units.
- Author
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Kim, Junhyun, Shin, Dongheok, Lee, Sungchan, Lee, Jaegyu, Kwon, Seongwoon, Yoon, Seulhee, Yoo, Do‐Sik, and Kim, Kyoungsik
- Subjects
- *
AUXETIC materials , *POISSON'S ratio , *DEFORMATIONS (Mechanics) , *HEXAGONAL crystal system , *CRYSTAL structure - Abstract
In this paper, we introduce methods of constructing structures with rigid sliding units that exhibit auxetic behavior, namely, have negative Poisson's ratio. First, we illustrate how we can construct 2-dimensional (2D) auxetic structures with bow-tie shaped rigid sliding hexagonal units. Next, we show that we can construct 3-dimensional (3D) auxetic structures by arranging hourglass shaped rigid sliding units in regular triangular configuration or in regular square configuration. Also, we show, through theoretical and numerical analysis, that these structures indeed exhibit auxetic behaviors. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
5. Analogies across auxetic models based on deformation mechanism.
- Author
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Lim, Teik-Cheng
- Subjects
- *
AUXETIC materials , *DEFORMATIONS (Mechanics) , *GEOMETRIC modeling , *CLUSTER theory (Nuclear physics) , *MATHEMATICAL models - Abstract
This paper reviews 2D auxetic models, including 3D deformation models with 2D auxetic behavior, from mechanism perspective instead of geometrical perspective. On this basis, auxetic models across different geometrical groups can be regrouped into clusters that exhibit analogy in deformation mechanism. Factors that are taken into consideration include the identification of corresponding (i) rotation and non-rotation units, as well as (ii) linkages/joints between rotation and non-rotation units and non-linkages/non-joints across various auxetic models. As a result, five clusters of auxetic models have been identified, in which auxetic models within each cluster are analogous to each other. The identified clusters are those that exhibit: (a) double periodicity in the rotation direction of their rotating units, (b) synchronized rotation direction of their rotation units, (c) single periodicity in the rotation direction of their rotating units, (d) random rotation of their rotation units, and (e) non-rotation of units. Results from this analogy identification place auxetic models in a systematic representation and will enrich future development of auxetic models, particularly those that do not fall within these five clusters. It is proposed that future work includes 3D auxetic models as well as ordering of analogous auxetic models according to their joints or linkage geometries. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
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